In recent years, development has been under way of a lawn mower of a type where a plurality of cutter blades is mounted on a blade disk drivable by a motor to rotate in a substantially horizontal plane. Such a lawn mower is popularly used as an unmanned self-propelled lawn mower (so-called robotic lawn mower), examples of which are disclosed in U.S. Pat. No. 8,234,848 (hereinafter referred to as “Patent Literature 1”) and European Patent Application Publication No. 2656720 (hereinafter referred to as “Patent Literature 2”).
The lawn mower disclosed in Patent Literature 1 includes: a rotation shaft extending in a vertical or up-down direction and drivable by a motor; a blade disk mounted on the rotation shaft; and a plurality of cutter blades formed integrally on the outer circumferential edge of the blade disk; and a blade protection section for protecting the cutter blades.
The lawn mower disclosed in Patent Literature 2 includes: a rotation shaft extending in a vertical or up-down direction and drivable by a motor; a blade disk mounted on the rotation shaft; and a plurality of cutter blades mounted on the blade disk; and a blade protection section for protecting the cutter blades.
In each of the aforementioned lawn mowers disclosed in Patent Literatures 1 and 2, the blade protection section comprises a cover shaped like a downwardly-opening pan and fixed to a machine body of the lawn mower. The blade protection section covers, from above, the entire blade disk and cutter blades, and the blade protection section has a lower end surface located beneath the plurality of cutter blades. Such a blade protection section is superior for protecting the cutter blades from hard projecting objects, such as stones and curbs, present on a lawn.
However, because the blade protection section disclosed in each of Patent Literatures 1 and 2 is constructed to cover, from above, the entire blade disk and cutter blades, it would unavoidably become relatively large in size and thus disadvantageously hinder an attempt to reduce the cost of the lawn mower. Besides, because the plurality of cutter blades is located above the lower end surface of the blade protection section, an effort to increase an amount of grass that can be cut at one time by the cutter blades would be limited. Therefore, further improvement has to be made for enhancing the grass cutting performance of the cutter blades.